— 29 — 
Verley-Boelsing), and at the same time endeavours to establish to 
what cause the difference in the results obtained by the various methods 
must be attributed. It is said to be solely due to the content of 
eugenol acetate in the oils of cloves, which, contrary to Erdmann's 
observations^), according to Spurge amounts to 7 to 1 7 per cent. 
The examinations made by Spurge have proved that with Umney's 
method the whole of the eugenol acetate contained in the oil of cloves 
is saponified quantitatively, and is consequently included in the esti- 
mation as eugenol, whereas in Thoms' method a partial saponification 
takes place, and in Verley-Boelsing's process only the free eugenol 
is determined. 
Spurge further states that he has found in mixtures of eugenol 
and clove oil terpene, that the correction indicated by Thoms is in- 
correct, and gives results which are too low by about 4 per cent. 2). 
If, in spite of this, the results obtained with oil of cloves according 
to Thoms agree well with those after Verley-Boelsing's method, 
this equalisation of errors must be attributed exactly to the partial 
saponification of the eugenol acetate which takes place in Thoms' 
process. 
In order to obtain comparable results by Umney's and Verley- 
Boelsing's methods. Spurge proposes to determine the percentage 
of eugenol acetate by the saponification of the oil of cloves in ques- 
tion, and to deduct the resulting acetyl rest^) from the eugenol-content 
found by Umney's method, or to add the eugenol-content ascertained 
from the saponification, to the result obtained according to Verley- 
Boelsing. These corrections, especially in the last-named case, are 
all the more important, as for the proper valuation of clove oil the 
eugenol present in the form of ester is also of importance. 
Spurge draws the conclusion that neither of the existing methods 
of eugenol-determination gives absolutely correct figures, but that in 
this respect preference should be given to Verley-Boelsing's method 
over the two others. He admits that the uncorrected modified method 
of Umney is also sufficiently exact to be used occasionally with 
advantage. 
Spurge endeavours to prove the correctness of the results obtained 
also by the fact that he calculates the specific gravities of the clove 
^) Journ. f. prakt. Chemie II. 56 (1897), 143. 
^) In examinations made by us years ago with mixtures of eugenol and the 
sesquiterpene of clove oil, the results differed only by i per cent. Comp. Report 
April 1892, 28. 
^) Spurge gives the following formula for the direct estimation of the per- 
a • 2 I 
centage of acetyl: ^/^ acetyl = a = the cc. semi-normal liquor used for saponi- 
fication ; s the quantity of clove oil used (in grams). 
